Set?

Select the correct com port from the dropdown menu on the left. Mine is COM17, yours is probably COM3 or COM4. If you plugged in your arduino after launching gcode sender, just hit the refresh circles next to the dropdown menu. That will rescan for new hardware.

When you've connected to your arduino you'll see something like this: $ dump settings. GREAT! That means we're talking to the arduino.

you might have to toggle the /n/r /n options at the top.

Go ahead and type '$' into the input box. This will dump GRBLs current settings to the screen.

Assuming you have set 8x Microstepping on the X&Y axis and full step on the Z Axis:

If something isn't set correctly, you can set it by typing the value you want (e.g. $0=87.49). Settings are stored in EEPROM and will be retained when the Arduino is turned off.

Go!

First, grab the gcode, some tape, and a piece of 1/4" thick cork.
Tape the cork down to the waste board in the middle of the work area. Make sure it is as flat as possible, and won't come loose during the job. Put a 1/8" end mill in the spindle, and tighten it down. The origin of the job is in the lower left hand corner, so center the ShapeOko over the lower left hand corner of the cork, and bring the Z-axis down until the end mill just touches the cork. That's zero. Turn on the spindle, take a deep breath, and stream the gcode. If all goes well, you'll end up with a sweet cork coaster!

There's also a video walkthrough of the process. You might consider watching it before you do this project.